Required practicals Flashcards
RP2- Calculating mitotic index of root cells.
Why is the onion/ garlic bulb suspended in water?
To stimulate cell division
RP2- Calculating mitotic index of root cells.
Why is root tip placed in ethanoic alcohol?
To stabilise the chromosomes
RP2- Calculating mitotic index of root cells.
Why is root tip placed in HCL and heated for 5 mins at 60 degrees
Helps separate cells by breaking down intracellular molecules
RP2- Calculating mitotic index of root cells.
Why are roots rinsed in water for 5 mins
To remove any HCL- ensuring chromosomes are not damaged
RP2- Calculating mitotic index of root cells.
Why are root tips pushed hard down on and why can no sliding occur
To ensure light can penetrate the cells- thin layer
Sliding will damage chromosomes
RP1- Investigation into the effect of a named variable on the rate of enzyme-controlled reaction
How will temperature be maintained
Use a thermostatically controlled water bath
RP1- Investigation into the effect of a named variable on the rate of enzyme-controlled reaction
How will amount of enzyme be controlled?
Use enzyme solutions of known concerntrations
Keep enzymes in same favourable conditions when storing
RP3- Production of a dilution series of a solute to produce a calibration curve to identify the water potential of plant tissue
Why can’t chips be too large?
Wont fit into tubes
RP3- Production of a dilution series of a solute to produce a calibration curve to identify the water potential of plant tissue
Why cant chips be too small?
Small inaccuracies are a higher proportion when dimensions are small
Calculating degrees of freedom Chi squared
Number of classes-1
Degrees of freedom Student T test
(n1-1) + (n2-1)
RP4- Investigation into named variable on cell membrane permeability
Why is beetroot washed before being added?
Removes pigment from damaged cells
Only pigment that leaves cells via membranes will be measured
RP4- Investigation into named variable on cell membrane permeability
Suggest why cylinders are 65 mm long
Enough cells to detect change in pigment
Not too big that beetroot wouldnt fit
RP4- Investigation into named variable on cell membrane permeability
Suggest why 25 cm^3 of water is added to each test tube
Enough to cover all beetroot cells
Not too much that the pigment is very diluted
RP4- Investigation into named variable on cell membrane permeability
Suggest why 25 cm^3 of water is added to each test tube
Enough to cover all beetroot cells
Not too much that the pigment is very diluted
RP5: Dissection of animal or plant gas exchange or mass transport system or of organ within such a system
How to reduce injury / infection
Cut away from body
When holding sharp items- hold downwards
Ensure to sterilise equipment after use
RP6- Effect of antimicrobial substances on microbial growth
Name some aseptic techniques
Wearing goggles and labcoats
Use bleach to clear area
Keep petri dish closed as much as possible
Use flame to sterlise equipment before use
Wash hands
RP6- Effect of antimicrobial substances on microbial growth
Why is mouth of beaker put in flame
The heat creates a convection current which drives air away from the bottle
Prevents air bourne microorganisms from entering
RP6- Effect of antimicrobial substances on microbial growth
Why is blue flame used rather than a yellow flame?
Blue flame is hotter-hot enough to kill microorganisms and cause air to move ou of bottle
RP6- Effect of antimicrobial substances on microbial growth
How does incubating dishes at room temperature reduce danger
Prevents growth of organisms which thrive at body temperature
Reduces chance of pathogenic bacteria forming
RP6- Effect of antimicrobial substances on microbial growth
What would make a suitable control experiment
Repeat paper disks soaked in water
Proves that it is antibiotic which kills the bacteria
RP6- Effect of antimicrobial substances on microbial growth
What needs to be controlled so that the results can be compared
Concentration of nutrients in agar
Temperature and pH
SPecies of bacteria
Time plates are left for
Concentration of antibiotics
RP8- The effect of wavelength of light on dehydrogenase activity in chloroplasts
What is the purpose of container of water between the lamp and experimental tubes
Acts as a heat sink
Prevents rate of reaction in tubes being affected by temperature
Prevents Enzymes from being denature
RP9- Investigation into the effect of a named variable on rate of respiration
What volume of water is ideal to use for water bath
1dm
Loses heat slowest
Needs water added less often
RP9- Investigation into the effect of a named variable on rate of respiration
Two solutions initially kept separate
Why?
Ensures whole reaction happens at measured temperature
Allows each solution to get to temperature
RP10- Investigation into the effect of an environmental factor on movement of an animal
Why is a teaspoon used to move woodlice instead of tweezers?
Tweezers unethical
May injure woodlice affectinng results
RP10- Investigation into the effect of an environmental factor on movement of an animal
Why does filter paper have to be replaced after each experiment
Woodlice may leave a residue which could affect the movement of the other woodlice in next experiment
RP10- Investigation into the effect of an environmental factor on movement of an animal
Why are woodlice replaced after each experiment
Different woodlice respond in differenrt ways
Ensures any anomalies have little effect on the results
RP12- Investigation into the effect of a named factor on the distribution of a living species
Why are quadrats placed randomly?
To ensure there was no bias
To ensure the results were representative of the sample
RP12- Investigation into the effect of a named factor on the distribution of a living species
What is a quadrat
A line over which measurements are made over several positions
Equation for dilution series volume
Volume of current stock=(final conc. neededXfinal volume needed)/initial concentration
